YES, you'll have to pay capital gains tax.
Using your figures and Single filing status:
Work income (excluding capital gain) $40,000 + LT capital gain $300,000 = Total taxable income $340,000.
Entire capital gain would be taxable at 15%, which =
$45,000 federal tax on the capital gain
Calculation does not include state capital gain tax, if any.
Here's a link to an online CG tax calculator. With the online calculator, enter your State of Residence and your Filing Status at the top of the page, and then enter your numbers. It will then calculate your state CG tax as well as the federal:
Capital Gains Tax Calculator 2021 | Casaplorer
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
